Enhanced growth of tellurium nanowires under conditions of macromolecular crowding.

An unprecedented rate enhancement was observed in the wet-chemical synthesis of tellurium nanowires under crowded conditions of inert macromolecules. The synthesis was carried out at 105 °C using solutions of sodium tellurite (Na2TeO3) as a precursor, hydrazine (N2H4) as a reducing agent, and polyvinylpyrrolidone (PVP) as both a stabilizing and crowding agent. The PVP concentration was systematically varied between the dilute and crowding regimes up to 166 g l-1. The growth of the nanowires was monitored by measuring their size-dependent optical properties in the UV-Vis spectrum characterizing the size and morphology evolution of the nanowires and a coexisting phase of amorphous tellurium nanoparticles. The observed growth characteristics were interpreted in terms of non-specific structural organization of the crowded media due to the entropic-driven effects of space compartmentalization.

Supercapacitors: An Efficient Way for Energy Storage Application.

To date, batteries are the most widely used energy storage devices, fulfilling the requirements of different industrial and consumer applications. However, the efficient use of renewable energy sources and the emergence of wearable electronics has created the need for new requirements such as high-speed energy delivery, faster charge-discharge speeds, longer lifetimes, and reusability. This leads to the need for supercapacitors, which can be a good complement to batteries. However, one of their drawbacks is their lower energy storage capability, which has triggered worldwide research efforts to increase their energy density. With the introduction of novel nanostructured materials, hierarchical pore structures, hybrid devices combining these materials, and unconventional electrolytes, significant developments have been reported in the literature. This paper reviews the short history of the evolution of supercapacitors and the fundamental aspects of supercapacitors, positioning them among other energy-storage systems. The main electrochemical measurement methods used to characterize their energy storage features are discussed with a focus on their specific characteristics and limitations. High importance is given to the integral components of the supercapacitor cell, particularly to the electrode materials and the different types of electrolytes that determine the performance of the supercapacitor device (e.g., storage capability, power output, cycling stability). Current directions in the development of electrode materials, including carbonaceous forms, transition metal-based compounds, conducting polymers, and novel materials are discussed. The synergy between the electrode material and the current collector is a key factor, as well as the fine-tuning of the electrode material and electrolyte.

A review on the production of 17-4PH parts using press and sinter technology.

The press and sinter method remains the standard among powder metallurgy processes for powdered stainless-steel materials. It delivers low cost, low oxidation rate, and adequate corrosion resistance. Furthermore, 17-4PH is a martensitic stainless-steel that is commonly used for high-strength and medium-ductility stainless steel parts. However, a few studies have investigated the press and sinter method for producing 17-4PH parts. This shortage is due to the high hardness (low compressibility) of 17-4PH powder. Thus, the main objective of this study is to evaluate the press and sinter method in terms of the manufacturing process, the influencing factors, and the theoretical basis of press and sinter methods in conjunction with metal injection molding technology for the production of 17-4PH parts. First, the literature and monographs are examined and summarized to cover the previous results, research progress, development trends, and applications of press and sinter method 17-4PH parts. Following the theoretical analysis, the practical investigation was conducted by producing parts with cold pressing from 800 to 1600 MPa, followed by sintering: the sintering temperature was 1200 °C for one hour under a protective vacuum atmosphere. ImageJ analysis was performed to measure the sinter density. The results showed an increase in relative sinter density from 84.43% to 96.43% for 800 and 1600 MPa, respectively, while the earlier results reached 93.47%. Overall, the press and sinter method enables the production of high-hardness 17-4PH parts with a high density, without using additives like lubricants, wax, or alloying elements.

Calcium silicate layer on titanium fabricated by electrospray deposition.

Titanium and its alloys have been used as implant materials. Non-ideal osseointegration of the implant materials has facilitated the development of the bioactive coatings on the implant surfaces. In this work, the bioactive calcium silicate (CaSi) powder prepared in a green synthesis route was used to cover the surface of Ti implants by a facile electrospray deposition method. Post annealing in air was also applied to form the oxidation layer on the Ti surface with the aim of increasing the bond strength between the CaSi coating layer and Ti substrate. For the characterization of the coatings several analytical methods such as X-ray diffraction, scanning electron microscopy, secondary neutral mass spectrometry, and Raman-spectroscopy were used, in addition to the measurement of bond strength and corrosion resistance. The results indicated a uniform CaSi layer with a thickness of about 1 µm deposited on the Ti substrate. Annealing in the range of 700-900 °C in air resulted in the formation of rutile phase of TiO2; more importantly, annealing at 800 °C did not significantly affect the composition of the CaSi layer consisting of ß-Ca2SiO4. The bond strength between the coating layer and Ti substrate can be remarkably enhanced at an annealing temperature of 700 or 800 °C compared with the as-prepared coating without annealing. The annealed coatings had a better corrosion resistance than the as-prepared coating. It is concluded that the electrospray method associated with the post-annealing can be successfully used for the deposition of a CaSi layer with a defined structure and composition on titanium implants.